(1) Field of the Invention
This invention relates to measuring instruments and more particularly to a pump which delivers an exact preset volume of gas for each stroke.
(2) Description of the Prior Art
Present commercial practice is to take samples from gas pipelines. There are numerous reasons for this, but the most common reason is when the ownership of the gas is being transferred, it is important to know the quality of the gas within the pipeline or other container. The quantity of the gas is also measured. Sampling devices commonly include a sample flask or container. The container is attached to a pumping device which pumps a fixed volume of gas at periodic intervals. Most common, the interval is picked as a periodic time interval, e.g., every 30 minutes. Normally, a pneumatic motor is used so that if a timing device produces a pressure pulse every 30 minutes, the motor will cause the sampling device to stroke once every 30 minutes.
To prevent contamination of the sample, the tubing of the sampling device to the flask is purged after an empty flask is connected. Also, to obtain an uncontaminated sample, the flasks are evacuated as near as possible when connected to the sampling device. Therefore, the pressure within the flasks will be far less than the pressure in the pipeline when first connected. Normally, the flasks will be connected to receive samples for an extended period of time; e.g., one week. At the end of the sampling period, the flasks will have much higher pressure than the pipeline.
U.S. Pat. No. 3,945,770, to Welker, discloses a sampling device intended to obtain a fixed amount of fluid each time the device is "stroked".
Before this application was filed, applicant caused a search to be made in the United States Patent and Trademark Office. Five patents were reported on the search, none of which appear to be pertinent to the applicant, but he is listing them herewith inasmuch as he believes that an Examiner would be interested in any patents reported by an experienced patent searcher. They are: Rogers U.S. Pat. No. 1,925,751 Lundeen U.S. Pat. No. 3,048,274 Berg U.S. Pat. No. 4,252,296 Graham U.S. Pat. No. 4,407,548 Aerd U.S. Pat. No. Re. 30,115.